class Student(object):
    def __init__(self, name, score):
        self.name = name
        self.score = score

    def get_grade(self):
        if self.score >= 90:
            return 'A'
        elif self.score >= 60:
            return 'B'
        else:
            return 'C'



lisa = Student('Lisa', 99)
bart = Student('Bart', 59)



print (bart,Student) # 实例和对象

print (bart.name,bart.score) # 实例属性


bart.age = 8 # 新增一个外部变量
print (bart.age)

